The present invention relates to a shaft device particularly suitable for a bellows-type gas meter comprising at least two eccentric cam assemblies, at least the first one of said eccentric cam assemblies being firmly coupled with a shaft and at least one other eccentric cam assembly being adjustable to alter the angle enclosed between the centerline of said first eccentric cam assembly and the centerline of said other eccentric cam assembly displaced relative to said first eccentric cam assembly.
A shaft assembly is provided in bellows-type gas meters for translating the forward and backward motion of diaphragms into a rotating motion then translated into the opening and closing motions of valves creating in a cyclic mode passages between the measuring chambers of such bellows-type gas meters and the gas inlets or gas outlets of such meters respectively. An alteration of the angle enclosed between the centerline of the first eccentric cam assembly and the centerline of the other eccentric cam assembly displaced relative to said first eccentric cam assembly is necessary for each valve to close before the diaphragm operating in conjunction therewith moves into its final position at the end of each filling cycle, thereby reducing the typical error of a bellows-type gas meter.
To alter said angle, one of said eccentric cam assemblies may be a flexible crank assembly, but the use of a flexible crank assembly is associated with the disadvantage of inaccuracy. It is also known from prior art that one of said eccentric cam assemblies may be coupled with a fork-type device fitted with prongs having setting screws acting upon a lever connected with the other eccentric cam assembly, an alteration of the angle thereby becoming relatively complicated.